Supplementation with Lactobacillus reuteri or L. acidophilus reduced intestinal shedding of cryptosporidium parvum oocysts in immunodeficient C57BL/6 mice.

The effect of L. acidophilus supplementation to reduce fecal shedding of Cryptosporidium parvum oocysts was compared to L. reuteri using C57BL/6 female mice immunosuppressed by murine leukemia virus (strain LP-BM5) inoculation. After 12 weeks post LP-BM5 inoculation, 15 immunosuppressed mice each were randomly assinged to one of the following treatment groups: historical control (group A), LP-BM5 control (group B), C. parvum (group C), L. reuteri plus C. parvum (group D) or L. acidophilus plus C. parvum (group E). Mice were pre-fed the L. reuteri or L. acidophilus bacteria strains daily for 13 days, challenged with C. parvum oocysts and thereafter fed the specified Lactobacillus regimens daily during the experimental period. Animals supplemented with L. reuteri shed fewer (p<0.05) oocysts on day-7 post C. parvum challenge compared to controls. Mice supplemented with L. acidophilus also shed fewer (p<0.05) oocysts on days 7 and 14 post-challenge compared to controls. Overall, Lactobacillus supplementation reduced C. parvum shedding in the feces but failed to suppress the production of T-helper type 2 cytokines [interleukin-4 (IL-4), IL-8)] which are associated with immunosuppression. Additionally, Lactobacillus supplementation did not restore T-helper type 1 cytokines (interleukin-2 (IL-2) and gamma interferon (IFN-gamma), which are required for recovery from parasitic infections. Altered T-helper types 1 and 2 cytokine production as a consequence of immunodysfunction permitted the development of persistent cryptosporidiosis while mice with intact immune system were refractory to infection with C. parvum. Reduction in shedding of oocysts observed in the Lactobacillus supplemented mice during deminished IL-2 and IFN-gamma production may be mediated by factors released into the intestinal lumen by the Lactobacillus and possibly other host cellular mechanisms. These observations suggest that L. reuteri or L. acidophilus can reduce C. parvum parasite burdens in the intestinal epithelium during cryptosporidiosis and may serve potential benefits as probiotics for host resistance to intestinal parasitic infections. L. acidophilus was more efficacious in reducing fecal shedding than L. reuteri and therefore may also have implication in the therapy of cryptosporidiosis during immunosuppressive states including human AIDS.

Effect of Lactobacillus reuteri on intestinal resistance to Cryptosporidium parvum infection in a murine model of acquired immunodeficiency syndrome.

Efficacy of Lactobacillus reuteri as a probiotic for the control of Cryptosporidium parvum infection was evaluated in C57BL/6 female mice that were immunosuppressed by intraperitoneal inoculation with the LP-BM5 leukemia virus. Four months after inoculation, mice developed lymphadenopathy, splenomegaly, and susceptibility to C. parvum infection. After daily prefeeding with L. reuteri (10(8) cfu/day) for 10 days, mice were challenged with 6.5 x 10(6) C. parvum oocysts and fed L. reuteri during the entire study. Mice supplemented with L. reuteri and challenged with C. parvum cleared parasite loads from the gut epithelium. However, unsupplemented animals developed persistent cryptosporidiosis and shed high levels of oocysts in the feces. L. reuteri feeding increased its colonization of the intestinal tract, which was inversely related to the fecal shedding of oocysts. These findings suggest that L. reuteri may help prevent C. parvum infection in immunodeficient subjects.

LP-BM5 virus causes changes in lactic dehydrogenase and oxygen radical production in splenocytes of C57BL/6J mice.

The LP-BM5 murine leukemia virus causes acquired immunodeficiency syndrome in C57BL/6J mice (MAIDS), similar to that of AIDS in humans. The objective of this study was to determine the effect of LP-BM5 viral infection on cellular activation and membrane integrity of splenocytes. Oxidative burst in splenocytes in response to exposure to PMA (20 microg/ml) was significantly higher (p<.02) in infected than in control mice at two weeks post-infection using luminol-enhanced chemiluminescence. By 13 weeks post-infection superoxide anion production in infected mice was significantly lower when compared to controls coinciding with decreased proliferative response to mitogens. The extent of cell membrane damage as indicated by lactic dehydrogenase (LDH) activity in serum was significantly higher in infected than in control mice (p<.001). The results from this study suggests that LP-BM5 virus causes an initial stimulation of cellular activity followed by a decreased cell activation characterized by decreased proliferation of splenocytes and decreased oxygen radical production. Decreased cell membrane integrity indicated by increased LDH activity may partly be responsible for these changes.

Changes in serum antioxidant concentrations during infection with caprine lentivirus.

We are currently using caprine arthritis encephalitis virus (CAEV) infection in goats as a model to understand changes in some clinical parameters and host response to infection with human immunodeficiency virus (HIV). The objective of this study was to measure changes in serum antioxidant activities in various age groups of goats infected with CAEV. Serum from CAEV-infected goats had significantly higher catalase activity (105.47 +/- 5.96 kU/l) than serum from healthy control goats (79.92 +/- 17.06 kU/l). Moreover, serum catalase activity increased with increase in the time after infection with CAEV. No change was observed in total superoxide dismutase (SOD) or glutathione peroxidase activity although CuZn SOD levels were elevated in infected goats. There was a positive correlation between serum catalase activity and hydrogen peroxide (H2O2) scavenging activity (r = 0.70, p < 0.05). In order to investigate cell membrane integrity, we determined lactate dehydrogenase (LDH) activity in infected goats. Although there was a transient increase in LDH no correlation was observed between increased serum catalase activity and LDH activity (r = 0.16, p > 0.05). We have earlier observed decreased oxyradical production in CAEV infected goats. This observed increase in serum catalase, a scavenger of endogenous free radicals such as H2O2 may be partly responsible for the observed decrease in oxygen radicals found in vivo.

Bovine neutrophil activation by culture fluid from Pasteurella haemolytica serotypes A1 and A11.

Neutrophil activation has been thought to contribute to the pathogenesis of fibrinous pneumonia caused by Pasteurella haemolytica serotype A1. The activation of bovine neutrophils by culture fluid from the pathogenic P. haemolytica serotype A1 and the non-pathogenic serotype A11 was compared. Logarithmic-phase bacteria of each serotype were incubated in RPMI 1640-medium for 3 h at 37 degrees C. The culture fluid was collected by centrifugation and concentrated by ultrafiltration. The concentrated culture fluids were then tested for their ability to induce chemotaxis and respiratory burst in bovine neutrophils. Chemotactic activity was of similar magnitude in response to both serotypes. An early chemiluminescence response occurred at 5 min at 1:100 dilution and a late peak at 11 min at 1:500 dilution for serotype A1. The early peak was absent at all dilutions tested for serotype A11. Maximal chemiluminescence response was observed at 1:25 dilution with serotype A11 while maximal response was seen at 1:500 dilution with the culture fluid from serotype A1. Superoxide anion release was greater in response to culture fluid from A1 than A11 at all dilutions tested. Leukotoxin activity was 50-fold higher in culture fluid from serotype A1 than in culture fluid from serotype A11. In this study, the ability of P. haemolytica to attract and activate bovine neutrophils was not restricted to the pathogenic serotype A1.

Pathogenic mechanisms of caprine arthritis-encephalitis virus.

Goats infected with caprine arthritis-encephalitis virus (CAEV) show chronic arthritis and cachexia, which are progressive in nature. The immunopathogenic mechanisms responsible for these progressive clinical symptoms have not been fully elucidated. Various haematological and immunological parameters were evaluated in experimentally-infected goats showing typical signs of CAEV-induced disease. Infected goats showed recurrent lymphocytosis that may be due to constant presentation of antigen by infected cells of a monocyte/macrophage lineage. The serum alkaline phosphatase and gamma-glutamyl transferase concentrations were elevated in infected goats, a characteristic of hepatic and bone disorders. All other serum chemistry parameters were similar between infected and control goats. Importantly, the serum tumour necrosis factor-alpha (TNF-alpha) levels were higher in infected goats. The cachexia seen in infected goats may be at least partly due to altered metabolism as a result of prolonged elevation of serum TNF-alpha levels. Depressed natural killer cell activity was observed in infected goats and may contribute towards the establishment of a persistent infection with CAEV.